1. Field of the Invention
The present invention relates to an image synthesis output apparatus which synthesizes a plurality of images that are stored in an image storage means and generates a synthetic image that is displayed in a single display screen. It also relates to an image synthesis output method and a program product for the same purpose. In addition, the present invention relates to an image synthesis display apparatus which generates and displays the synthetic image, and portable communication equipment which includes the image synthesis display apparatus.
2. Description of the Related Art
As an image synthesis output apparatus according to a prior art, there is known, for example, the one which is incorporated in a computer system, as described in Japanese Unexamined Patent Publication No. 2000-259140 specification. FIG. 18 is a block diagram, showing the configuration of the main part of this computer system 900. The computer system 900 includes, as its primary elements, a personal computer (hereinafter, suitably described simply as the “PC”) 910, and a display monitor 920. The computer system 900 includes various component parts except them. However, those component parts are not directly related to the present invention, and thus, they are omitted.
The computer system 900 executes a multi-step power-saving control of the display monitor 920, using a VRAM-state notification signal 932. The VRAM-state notification signal 932 shows whether or not there is writing access to a video RAM 914 for forming an image (in this specification, “image data” which is a signal that expresses an image is also suitably described as the “image”). The PC 910 includes a display control section 912, and the display control section 912 is provided with a display controller 913 and the video RAM 914. The display control section 912 transmits, to the display monitor 920, the VRAM-state notification signal 932, as well as a video signal 931 which is an image for display.
The display controller 913 controls a display operation of the display monitor 920. It reads an image from the video RAM 914 at a certain screen refresh-rate. Then, it converts the image into a video signal 931 which has the three primary colors of R-G-B for display, and outputs it to the display monitor 920. The video RAM 914 stores an image which is displayed in the display monitor 920. It receives writing access by the control of software which is executed in the PC 910. Writing access is given to the video RAM 914, and thereby, the data or image which is stored in the video RAM 914 is rewritten. As a result, the image which is displayed in the display monitor 920 is updated.
If writing access is given to the video RAM 914, the VRAM-state notification signal 932 changes from “0” to “1”. Thereby, the display monitor 920 is notified that the writing access has been executed. If the writing access to the video RAM 914 is completed, the VRAM-state notification signal 932 returns to its former state of “0”.
While the PC 910 is executing processing, writing access to the video RAM 914 is executed each time an image is formed by the software control. However, while the PC 910 stays in an idle state, such as on standby for a key input, an image formation processing is not usually executed by the software control. The display monitor 920 refers to the change from “0” to “1” of the VRAM-state notification signal 932 and its return from “1” to “0”. Thereby, the state of writing access to the video RAM 914 by the PC 910 can be detected.
The display monitor 920 is an external display unit which is connected to the PC 910, such as a CRT monitor. The display monitor 920 includes, for power-saving control, a timer 921 and a power-down control section 922. Based on the VRAM-state notification signal 932 which it receives, the timer 921 measures the time which elapses after the writing access to the video RAM 914 has stopped. In other words, it measures the time which elapses after the PC 910 has become idle, thus the image which is stored in the video RAM 914 has not been updated, and thereby, the image which is displayed in the display monitor 920 has not been updated.
If the VRAM-state notification signal 932 becomes “1”, or if the timer 921 is reset by a system reset or the like, then the timer 921 starts a time-counting operation. This time-counting operation continues until the VRAM-state notification signal 932 becomes “1” again and is received. The power-down control section 922 executes a multi-step control of the display of the display monitor 920, according to the length of the time which is measured by the timer 921, or the time which elapses after the update of an image has stopped. Specifically, the longer the time which elapses after the update of an image has stopped becomes, the lower power-consumption state the display will be shifted into, step by step, from an ordinary display state, a low brightness state and a display-off state to a power-off state.
Hence, in the computer system 900, instead of measuring the time which elapses after a key input has not been executed, the PC 910 notifies, using the VRAM-state notification signal 932, the display monitor 920 whether or not there is writing access to the video RAM 914. Based on the VRAM-state notification signal 932, the display monitor 920 measures the time which elapses after the update of the image has stopped, or the time which elapses after the writing access for image formation to the video RAM 914 has stopped. According to the time which has elapsed, a multi-step power-saving control is executed. Thereby, the display monitor 920 can take the lead in controlling its display state step by step. As a result, in the computer system 900, the processing load on the PC 910 becomes lighter than that of a computer system in which a personal computer takes the lead in controlling and determining the display state of the display monitor 920.
However, a conventional image synthesis display apparatus executes a power-saving control only at the stage of displaying an image. In other words, a power-saving control is not considered at the stage of synthesizing and creating an image to be displayed. For example, in an image synthesis display apparatus which is incorporated in the computer system 900, a power-saving control of the display monitor 920 is executed at the time when an image is not updated. However, the power conservation of the display control section 912 in the PC 910 is not taken into account at all.